Clamping element for a fuel injection valve and fuel injection system

ABSTRACT

A clamping element for a fuel injector is provided that is insertable into a mounting hole of a cylinder head of an internal combustion engine, and that directly injects fuel into a combustion chamber of the internal combustion engine has a first step ring. This at least partially surrounds the fuel injector and has a valve pressure surface that may rest on the fuel injector. The first step ring has at least one circumferential slope surface on its side facing away from the valve pressure surface, which engages with a corresponding circumferential slope surface of a second step ring, which has a counterpressure surface. The slope surfaces are arranged so that the first step ring and the second step ring are pressed axially apart when they are rotated relatively to one another.

FIELD OF THE INVENTION

The present invention relates to a clamping element and a fuel injectionsystem.

BACKGROUND INFORMATION

A clamping element in the form of a hold-down element is referred to inJapanese Published Patent Application No. 08-312503. The hold-downelement holds down a fuel injector against a relatively high combustionpressure prevailing in the combustion chamber of the internal combustionengine. The hold-down element engages with a collar of the fuel injectorat two circumferentially opposite locations, the collar resting with itslower side on the upper side of the cylinder head, so that the fuelinjector is held down. The hold-down element is pulled on to thecylinder head by a clamping screw.

It is believed that the hold-down element referred to in JapanesePublished Patent Application No. 08-312503 has the disadvantage that itis difficult to access the clamping screw if a fuel distribution linehas already been fitted. If the fuel distribution line is not fitteduntil after the hold-down elements have been fitted and after they havebeen pre-tensioned to the defined retention force, the fuel injectorsmay no longer be moved or may only be moved if considerable force isapplied, and tolerances at the connection points to the fueldistribution line, which in the case of high-pressure injection systemsis rigid, may not be modified. Furthermore, a tight connection may onlybe achieved with difficulty or not at all. If the clamping screws arenot tightened until after the fuel distribution line has been fitted, itmay be difficult to access the clamping screws.

Furthermore, a hold-down device embodied as a clamp bracket similarhold-down element referred to in Japanese Published Patent ApplicationNo. 08-312503, is referred to in German Published Patent Application No.197 35 665. In the case of the hold-down device, the cylinder head has arecess in which the collar of the fuel injector is arranged, so that thecollar of the fuel injector on which the hold-down device acts islowered into the cylinder head. It is believed that this has thedisadvantages already mentioned.

A clamping element that holds a fuel injector in a mounting hole of acylinder head of an internal combustion engine and rests against a fueldistribution line, is referred to in German Published Patent ApplicationNo. 197 56 102. The clamping element includes a spiral spring thatextends between a spring holding element of the fuel injector and aspring holding element of the fuel distribution line. Furthermore, fromGerman Published Patent Application No. 197 56 102, for assembly, one ormore assembly clamps, which pre-tension the fuel injector, the fueldistribution line and the spiral springs and hold them in their positionuntil assembly has been completed, should be provided.

It is believed that a disadvantage of the clamping element referred toin German Published Patent Application No. 197 56 102 is that with aspiral spring it may be difficult to achieve the necessary high clampingforces. Furthermore, it may be disadvantageous that, if a pre-mountedunit that includes a fuel distribution line, clamping elements and fuelinjectors is fitted, additional assembly clamps may be required.Moreover, it may be disadvantageous that, when the fuel distributionline is fitted all spiral springs should be tensioned simultaneously andadjustments of individual fuel injectors to any tolerances in themounting hole in question may not be carried out consecutively.

SUMMARY OF THE INVENTION

By contrast, it is believed that an exemplary clamping element accordingto the present invention has the advantage that high clamping forces maybe achieved using small clamping element dimensions.

It is believed to be advantageous if the first step ring and the secondstep ring have coaxial holes into which the fuel injector and aconnection piece of a fuel distribution line may be inserted. Thus,small design dimensions and a favorable arrangement of the clampingelement may be achieved because only one circumferential collar aroundthe fuel injector is required to bear the clamping force. Furthermore,it is believed to be advantageous that the clamping element may be heldin the holes.

It is believed to be advantageous if the first step ring and the secondstep ring are held so that they are concentric relative to one anotherby shoulder of the first step ring or second step ring that engages witha corresponding step of an axial hole of the other step ring. As aresult, the clamping element may be a compact, self-contained component,which may be inserted as a single element during assembly.

It is believed to be advantageous if the first step ring and the secondstep ring each have on their circumference a bolt that is rotatablymounted axially parallel to the step ring and is axially movable, andhave a hole that extends across it, and if the hole of one bolt is athreaded hole, and if a screw that is held in the hole of the other boltis present and engages with the threaded hole. Thus, the first andsecond step ring may be rotated against one another and the clampingforce of the clamping element may be adjusted. For example, the screwmay be arranged so that it is easily accessible, as the axis of thescrew points away from a plane that is at least approximately formed bythe fuel injectors and the fuel distribution line and does not lie inthat plane.

It is believed that an exemplary fuel injection system according to thepresent invention has the advantage relative to the related art that theretention force is imparted against the fuel distribution line. As aresult, no additional components may be required, which may save space.Moreover, the sequence of tensioning may be chosen freely.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a clamping element via which a fuel injector is clampedinto a mounting hole.

FIG. 2 shows an exemplary clamping element according to the presentinvention installed between a fuel distribution line and a fuelinjector.

FIG. 3 is a sectional view of the exemplary clamping element accordingto the present invention shown in FIG. 2 with fuel a distribution line.

FIG. 4 is a sectional view showing further detail of portion IV shown inFIG. 3.

FIG. 5 is a sectional view of the exemplary clamping element of FIG. 2,with a tensioning device formed by a screw.

FIG. 6 shows an exemplary clamping element according to he presentinvention installed between a fuel distribution line and a fuelinjector, shown in a side view that has been rotated by 90° relative tothe exemplary embodiment shown in FIG. 2.

DETAILED DESCRIPTION

FIG. 1 shows a clamping element. The clamping element is in the form ofa hold-down element 1, which holds a fuel injector 2 in a mounting hole3. Fuel injector 2 is connected to a rigid fuel distribution line 4, forfuel injectors that inject fuel at high pressure into the combustionchamber. Hold-down element 2 has a contact piece 5, which rests on acylinder head 6 (shown here in section view, and only partly shown) andhas an attachment element that is embodied as screw 7. Screw 7penetrates a lever arm 8 of hold-down element 1 and is screwed into athreaded hole 9 of cylinder head 6.

Lever arm 8 divides in the shape of a fork around fuel injector 2. Fuelinjector 2 has a step 10, on whose radial surface pressure mushrooms 11,which are formed on the ends of the fork-shaped section of lever arm 8of hold-down element 1, rest. If it is rotated deeper into threaded hole9, screw 7 pulls lever arm 8, which rests against cylinder head 6 viacontact piece 5, toward cylinder head 6 via a washer 12, which allowsangle compensation via a spherical surface 13. As a result, at thefork-shaped end of lever arm 8 a clamping force is exerted on fuelinjector 2 in the direction of mounting hole 3 via pressure mushrooms 11(only one can be seen in the chosen view in the drawing) at two pointsof step 10 that are located opposite one another on the circumference offuel injector 2. This clamping force holds fuel injector 2 in mountinghole 3 against the combustion pressure in the combustion chamber (notshown).

FIG. 1 also shows connector plug 14 for triggering fuel injector 2 andseal 15 opposite the combustion chamber. Fuel distribution line 4 isconnected to fuel injector 2 via connector nozzle 14 a.

There may be little space, for example, next to and above the cylinderhead, since it is desirable for the design of the internal combustionengine to be compact. As a result, fuel distribution line 4 is arrangedas directly as possible above fuel injectors 2 and is generally offsetsomewhat from the middle of the cylinder head. This results in thearrangement shown in FIG. 1, in which the extension of central axis 16of screw 7 intersects with fuel distribution line 4. As a result, oncefuel distribution line 4 has been installed, a tool may be onlyintroduced laterally and with freedom of movement in one plane. This maybe hindered by other components, such as, for example, the ignition orgas exchange system.

FIG. 2 shows an exemplary clamping element according to the presentinvention that is arranged between a fuel distribution line 17 (onlypartly shown) and a fuel injector 18 (only partly shown), which isinserted into a cylinder head 26. A first step ring 19 has a valvepressure surface 20, which rests indirectly against fuel injector 18. Onthe side facing away from fuel injector 18 and valve pressure surface20, first step ring 19 has a plurality of circumferential slope surfaces21, which are arranged in one direction circumferentially, have the sameincline, and each form a section of a screw surface.

A second step ring 22 has a counterpressure surface 23, which restsagainst a shoulder of fuel distribution line 17. On the side facing fuelinjector 18, second step ring 22 also has a plurality of circumferentialslope surfaces.

Counterpressure surface 23 rests against a connection piece 25 of fueldistribution line 17. Furthermore, a central axis 27, which correspondsto the axis of the mounting hole (not shown) of fuel injector 18 incylinder head 26, is also shown in the drawing. Circumferential slopesurfaces 21, 24 of first step ring 19 and of second step ring 22 matchone another in their incline and orientation of rotation so that theywork together as a thread and, respectively, engage with one another viatheir slope surfaces 21, 24. Incline surfaces 21, 24 may, for example,resemble the teeth of a saw.

FIG. 2 also shows a connector plug 28 of fuel injector 18, which in theembodiment shown in FIG. 2 is a fuel injector 18 having an electricallytriggered actuator. Furthermore, FIG. 2 shows parts of a tensioningdevice 29 (largely hidden) which allows first step ring 19 and secondstep ring 22 to be rotated relative to one another and which isdescribed in detail with respect to FIG. 5 below.

In the non-tensioned state shown in FIG. 2, individual circumferentialslope surfaces 21 of first step ring 19 are in contact with thecorresponding circumferential slope surfaces of second step ring 22 sothat every circumferential slope surface 21, 24 is in contact with acorresponding circumferential slope surface 21, 24 over its entiresurface. If first step ring 19 and second step ring 22 are rotatedrelative to one another, circumferential slope surfaces 21, 24 slideagainst each other and push first step ring 19 and second step ring 22apart. Valve pressure surface 20 and counterpressure surface 23 move inthe axial direction relative to central axis 27.

If valve pressure surface 20 rests on fuel injector 18 andcounterpressure surface 23 rests on connection piece 25 of fueldistribution line 17, the clamping element presses fuel injector 18 intomounting hole of cylinder head 26, and rests against fuel distributionline 17. If the incline of the circumferential slope surfaces 21, 24 isappropriately chosen, the compressive force exerted may be determined asa function of the force with which first step ring 19 and second stepring 22 are rotated relative to one another. In particular, substantialcompressive forces may be achieved.

The maximum distance in the axial direction relative to central axis 27by which first step ring 19 and second step ring 22 may be pressed apartmay be determined by the number of circumferential slope surfaces 21, 24and the incline. Thus, substantial tolerances may be offset in the axialdirection relative to central axis 27 that arise between fueldistribution line 17 and fuel injector 18. Furthermore, the clampingelement does not require any further attachment point on cylinder head26, like screw 7 in FIG. 1 in the case of a hold-down element.Altogether, the dimensions of an exemplary clamping element according tothe present invention may be small.

FIG. 3 shows the exemplary clamping element according to the presentinvention shown in FIG. 2 in a sectional view, fuel distribution line 17being partially shown in a sectional view. In FIG. 3, the same referencenumbers are used as in FIG. 2 for the same elements. Fuel injector 18,which is inserted into cylinder head 26, is also only partly shown.Connection piece 25 of fuel distribution line 17 is connected via aninflow hole 35 to a distribution pipe 34 of fuel distribution line 17.Central axis 27, which is shown in the FIG. 3, corresponds to the axisof the mounting hole (not shown) of fuel injector 18 in cylinder head26.

Moreover, connection piece 25 has a smaller-diameter shoulder 36, whichis held in a coaxial hole 31 of first step ring 19 and in a coaxial hole32 of second step ring 22, which have the same diameter. Thus, theclamping element is defined radially relative to central axis 27 withregard to connection piece 25 of fuel distribution line 17.

Fuel injector 18 is inserted into a hole 38 of connection piece 25 offuel distribution line 17 via an inflow section 37. A ring seal 39 sealsinflow section 37 of fuel injector 18 against hole 38 of connectionpiece 25. Fuel injector 18 has a clamping sleeve 40 (shown in asectional view), on which first step ring 19 rests and which has arecess, e.g., in the area of connector plug 28. This clamping sleeve 40and fuel injector 18 may be a single component. FIG. 3 also showsconnector plug 28 of fuel injector 18, which in the embodiment shown inFIG. 3, is a fuel injector 18 having an electrically triggered actuator,and also partially shows tensioning device 29, which is explained indetail with respect to FIG. 5 below.

FIG. 4 shows detail section IV from FIG. 3. First step ring 19 restsagainst clamping sleeve 40 of fuel injector 18 via valve pressuresurface 20. Second step ring 22 rests on a shoulder 30 of connectionpiece 25 of fuel distribution line 17 via counterpressure surface 23.Circumferential slope surface 21 of first step ring 19 andcircumferential slope surface 24 of second step ring 22 are formed sothat radially inward they do not reach coaxial hole 31 of first stepring 19 and coaxial hole 32 of second step ring 22. First step ring 19has a shoulder 33, which is held in a step 41 of coaxial hole 32 ofsecond step ring 22.

Fuel injector 18 and connection piece 25 of fuel distribution line 17may be inserted into one another. The seal created by ring seal 39 maybe checked when a pre-mounted unit that includes fuel injector 18, theclamping element and fuel distribution line 17 is produced because, inthe non-tensioned state, the exemplary clamping element according to thepresent invention may not exert any force on fuel injector 18 and fueldistribution line 17, and therefore the components remain in theposition relative to one another that they were in when checked.Furthermore, the exemplary clamping element according to the presentinvention may have small dimensions and be held by concentric holes 31,32 and smaller-diameter shoulder 36 of connection piece 25. Moreover,shoulder 33 of first step ring 19, which is held in step 41 of coaxialhole 32 of second step ring 22, may help ensure that circumferentialslope surfaces 21, 24 are unable to move radially relative to oneanother.

FIG. 5 shows a top view of second step ring 22 across section plane V ofFIG. 2. The parts of fuel injector 18 and connection piece 25 of fuelinjection line 17 that are located inside coaxial holes 31, 32 of firststep ring 19 and of second step ring 22 are not shown. As shown in FIG.5, first step ring 19 is hidden by second step ring 22. Tensioningdevice 29 includes a first double eye 42, which is attached to firststep ring 19, and second double eye 43, which is attached to second stepring 22. A first bolt 44 is rotatably and axially movably mounted infirst double eye. 42. Correspondingly, a second bolt 45 is rotatably andaxially movably mounted in second double eye 43. Second bolt 45 has athreaded hole into which a screw 46 is inserted so that it extendstransversely. Screw 46 is held in a hole of first bolt 44 and restsagainst first bolt 44 via a screw head 47.

If this screw is rotated into the threaded hole of second bolt 45, screwhead 47 pulls second bolt 45 in the direction of first bolt 44. Firststep ring 19 and second step ring 22 are rotated relative to one anothervia first double eye 42 and second double eye 43 and the clampingelement is tensioned. As first step ring 19 and second step ring 22 moveapart in the direction of the axes of bolts 44, 45, there may be atendency for screw 46 to tilt in the threaded hole of second bolt 45 andthe hole of first bolt 44. To avoid this tendency, bolts 44, 45 areaxially movable, and therefore may compensate for the movement apart offirst step ring 19 and second step ring 22.

FIG. 6 shows a side view of an exemplary clamping element according tothe present invention installed between a fuel distribution line 17(only partly shown) and a fuel injector 18 (only partly shown) rotatedby 900 relative to the side view in FIG. 2. The same reference numbershave been used for the same components.

FIG. 6 shows fuel injector 18 having connector plug 28 and cylinder head26. First step ring 19 and second step ring 22 are located betweenconnection piece 25 of fuel distribution line 17 and fuel injector 18.First bolt 44 is held in first double eye 42, which is connected tofirst step ring 19. Screw head 47 rests against this first bolt 44.First bolt 44 may be moved in the direction of its axis in first doubleeye 42.

Screw head 47 is easily accessible with a tool because, as shown in FIG.6, it may be arranged so that it points away from the internalcombustion engine. The screw head 47 may be easily reached, since screwhead 47 is not covered by other components and is reachable with anappropriate tool.

What is claimed is:
 1. A clamping arrangement for a fuel injector, whichis insertable into a mounting bole of a cylinder head of an internalcombustion engine to directly inject fuel into a combustion chamber ofthe internal combustion engine, the clamping arrangement comprising: afirst step ring at least partially surrounding the fuel injector andresting on the fuel injector via a valve pressure surface, the firststep ring including at least one first circumferential slope surface ona side of the first step ring facing away from the valve pressuresurface; and a second step ring including at least one secondcircumferential slope surface and a counterpressure surface; wherein theat least one first circumferential slope surface of the first step ringengages with the at least one second circumferential slope surface ofthe second step ring, and the at least one first circumferential slopesurface of the first step ring and the at least one secondcircumferential slope surface of the second step ring are arranged sothat the first step ring and the second step ring are pressed axiallyapart when rotated relatively to one another.
 2. The clampingarrangement of claim 1, wherein each of the first step ring and thesecond step ring includes coaxial holes into which the fuel injector anda connection piece of a fuel distribution line are insertable.
 3. Theclamping arrangement of claim 2, wherein at least one of the first stepring and the second step ring is held in the coaxial holes by asmaller-diameter shoulder of the connection piece of the fueldistribution line.
 4. The clamping arrangement of claim 1, wherein thefirst step ring and the second step ring are held concentrically withrespect to each other by a shoulder of one of the first step ring andthe second step ring, the shoulder engaging with a corresponding step ofan axial hole of the other step ring.
 5. The clamping arrangement ofclaim 1, wherein the first step ring and the second step ring are heldconcentrically relative to one another by a sleeve situated in a commonaxial hole of the first step ring and the second step ring.
 6. Theclamping arrangement of claim 1, further comprising a tensioning device,wherein each of the first step ring and the second step ring includes atensioning element on its circumference, the tensioning device isprovided between the tensioning elements of the first step ring and thesecond step ring, the first step ring and the second step ring beingaxially pressed apart if the tensioning elements are pulled toward oneanother.
 7. The clamping arrangement of claim 6, wherein each of thetensioning elements includes a bolt rotationally mounted so that an axisof the bolt is parallel to an axis of a corresponding step ring, each ofthe bolts being axially movable and penetrated by a transverse hole. 8.The clamping arrangement of claim 7, wherein the transverse hole of oneof the bolts includes a threaded hole, and the tensioning deviceincludes a screw held in the transverse hole of the other bolt andengaging with the threaded hole.
 9. The clamping arrangement of claim 8,wherein the tensioning device is positioned on the circumference of thefirst step ring and the second step ring so that one axis of the screwis approximately perpendicular to a plane defined at least approximatelyby a rigid fuel distribution line along its longitudinal extension andby the fuel injector connected to it.
 10. The clamping arrangement ofclaim 1, wherein the at least one first circumferential slope surface ofthe first step ring and the at least one second circumferential slopesurface of the second step ring resemble teeth of a saw.
 11. A fuelinjection system comprising: a fuel distribution line; fuel injectorsfor directly injecting fuel into combustion chambers of an internalcombustion engine, the fuel injectors connected to the fuel distributionline via connection nozzles, the fuel injectors insertable into mountingholes of a cylinder head of the internal combustion engine; and clampingelements, each of the clamping elements at least partially surrounding acorresponding fuel injector and including a first step ring at leastpartially surrounding the corresponding fuel injector and resting on thecorresponding fuel injector via a valve pressure surface, the first stepring including at least one first circumferential slope surface on aside of the first step ring facing away from the valve pressure surfaceand a second step ring including at least one second circumferentialslope surface and a counterpressure surface; wherein the at least onefirst circumferential slope surface of the first step ring engages withthe at least one second circumferential slope surface of the second stepring, and are arranged so that the first step ring and the second stepring are pressed axially apart when rotated relatively to one another.